Air circuit breakers as described within U.S. Pat. Nos. 3,095,489 entitled "Manual Charging Means for Stored Energy Closing Mechanisms of Electric Circuit Breakers" and 3,084,238 entitled "Ratchet Mechanism for Charging a Closing Spring in an Electric Circuit Breaker" include operating mechanisms that are mainly exposed to the environment. Since the air circuit breakers are rated to carry several thousand amperes of current continuously, the exposure to convection cooling air assists in keeping the operating components within reasonable temperature limits.
Such air circuit breakers are usually provided with a motor operator such as described in U.S. Pat. No. 4,167,988 entitled "Ratcheting Mechanism for Circuit Breaker Motor Operator" or a manual handle as described in U.S. Pat. No. 3,729,065 entitled "Means for Charging A Stored Energy Circuit Breaker Closing Device" for charging the powerful closing springs contained within the air circuit breaker operating mechanism.
As described within the aforementioned U.S. Pat. No. 4,167,988, the ratchet mechanism includes a driving pawl coupled with the motor operator for incrementally advancing a ratchet wheel coupled with the circuit breaker operating mechanism. Each incremental advance of the ratchet wheel is sustained by a holding pawl. Ultimately, the ratchet wheel is advanced to an angular position where the circuit breaker closing springs are fully charged and therefore empowered to forcibly close the circuit breaker contacts. Typically, the discharge of the closing springs rapidly drives the ratchet wheel in the same direction as did the driving pawl in charging the closing springs. In the process, the teeth on the ratchet wheel impact with the driving and holding pawls, producing undue pawl and ratchet wear, as well as unnecessary stress on the pawl springs and mountings. Moreover, when the breaker contacts close, there is an inevitable rebound which tends to rotate the charging gear in a reverse direction. Under these circumstances, the straight sides of the ratchet teeth impact against the straight edges of the pawl tips, causing potentially damaging stresses in the ratcheting mechanism. The patent further suggests the use of a holding prop to hold the pawls out of engagement with the ratchet wheel until the closing springs have fully discharged to protect the pawls and the ratchet wheel from potential damage. When the contacts have become closed, the circuit breaker operating mechanism components are exposed to allow an operator to manually release the holding prop in order for the holding pawl to again become operative in re-charging the circuit breaker closing spring.
When the circuit breaker closing springs are brought to their fully-charged conditions, it is important that the springs do not become inadvertently discharged while an operator has hold of the charging handle in order to avoid damage to the ratchet mechanism and the associated air circuit breaker contacts. An early arrangement of a latching means to prevent rotation of a closing springs charging handle is found in U.S. Pat. No. 4,475,021 entitled "Air Circuit Breaker".
The motor operated circuit breaker and manual variation thereof both employ a common operating mechanism and contact arrangement such that either the motor variation of the ratcheting mechanism or the manual ratcheting mechanism is installed during the manufacturing process, usually at the time of installation of the operating mechanism. It would be advantageous to have a modular ratcheting mechanism whereby a common platform with minor variation could be employed with either a motor-operated circuit breaker, a manual circuit breaker or a combination thereof.
When a manual ratcheting mechanism is employed, there is a large force concentration on the manual operating handle, particularly in the vicinity of the operating handle pivot. Tale operating handle components are usually made of hardened steel to resist bending or wear over long periods of continuos use. The use of a simple inexpensive operating handle structure has heretofore been avoided.
One purpose of the invention is to provide a modular ratcheting mechanism that will fit the requirements of either a motor operator driven circuit breaker closing spring, a handle operator driven circuit breaker closing spring or a combination of both with minor adjustment to the ratcheting mechanism.
A further purpose of the invention is to utilize a simple and inexpensive circuit breaker operating handle capable of withstanding several thousand pounds of force without failure over long periods of continued usage.
A further purpose of the invention is to provide a means to disengage the charging pawl when the closing springs are released without damaging the charging system.